1. Technical Field
This invention relates generally to digital control and, more particularly, to adaptive digital control of an electronic device in response to a rotary digital switch input.
2. Discussion
Electronic sound systems such as radios commonly employ pushbutton or rotary controls to manually vary the system operation. Pushbutton controls offer a quick response but generally are not all that versatile since values between the preset parameter values are generally not available. Conventional analog controls have included the use of rotary potentiometers and variable resistors which offer the advantage of an infinitesimal adjustment capability, but generally do have drawbacks associated therewith. Over time the potentiometer will typically gather surface film, accumulate dust and the operation will tend to become noisy, open and/or intermittent.
In order to use an analog control with a microcomputer, an analog to digital converter is generally required to convert the analog voltage to a digital voltage. Modern radios and, in particular, those employed in automobiles tend to employ microcomputer control technology. Thus, it is generally desirable to have controls which can easily interface with a microcomputer and advantageously utilize the superior digital control capabilities associated therewith.
It is generally known to use a rotary switch with a digital output as a radio volume control or a tuner selector in a microcomputer controlled system. Such a rotary switch can be rotated in either a clockwise or counter-clockwise direction to close switch contacts which are arranged in fixed angular increments. Each switch contact position outputs one of three digital numbers according to a predetermined sequence. By evaluating the change in the numbers during rotation, the microcomputer can determine the direction of rotation and the amount of rotation and then change the tuning or volume control signal accordingly. This is generally accomplished without noise interference or other adverse effects commonly associated with prolonged use and aging for other types of switches.
A disadvantage of the conventional rotary switch arrangement is that for a tuner control each angular increment must result in a signal change small enough for tuning to every station, and consequently much rotation is required to traverse the entire tuning bandwidth of the radio. This limitation is particularly annoying in the case of a volume control. It is sometimes desirable to quickly change the volume to reach the sound level that is most enjoyable to the user. Say, for instance when first turning on the radio system, the previous user has left the volume control set to a highly uncomfortable audio level. The present user would like to have the ability to quickly reduce the audio level to a more comfortable level. Yet, it is also desirable to have the ability to make small volume adjustments. Thus, it is desired to have both fine and coarse control with the same control switch.
It is therefore one object of the present invention to provide for a digital control for an electronic radio which has functions controlled in response to a rotary switch that produces a digital control signal.
It is another object of the present invention to provide for an enhanced digital control which enables a user to variably control the volume of a radio via a digital switch.
It is a further object of the present invention to provide for such an enhanced digital control which enables a user to variably control a tuner selector of a radio via a digital switch.
Yet, it is still a further object of the present invention to provide for both fine and coarse control capability to handle the above operations with a single digital switch for each control function.